FIG. 1 shows a prior art dental restorative system described in U.S. Pat. No. 5,685,714 entitled xe2x80x9cSupport Post for Use in Dental Implant System.xe2x80x9d The system generally includes a dental implant 10 and a support post or abutment 12. The implant is embedded into the jawbone leaving a gingival end 14 exposed through the bone. This gingival end includes a threaded recess 15 and a multi-sided male projection 16 for abutting with the abutment 12.
The abutment has a cylindrical configuration with an elongated upper portion 18 and a lower transgingival portion 20. The abutment serves several functions but generally provides a structure for extending the implant above the gum-line. In this regard, one end of the abutment connects to implant while the other end connects to a prosthesis 22.
A passageway 24 extends through the abutment and provides a recess 26 at the transgingival portion 20 for engaging the projection 16 of the implant. A screw 28 abuts against a shoulder 30 and engages the threaded recess 15 to hold the abutment to the implant. The prosthesis 22 is fabricated around the upper portion and typically connects to the abutment with either a separate screw (not shown) or cement.
Typically, the abutment is made of metal, such as titanium. An entirely metallic abutment, however, can be visible through the prosthesis and can result in a dark, unattractive shadow within the prosthetic structure. In order to alleviate this particular problem, the abutment shown in FIG. 1 is made from two different materials. An outer portion 34 is made from ceramic and an inner portion, shown as an insert 36, is made from titanium or its alloys. The ceramic shields the shadow of the metallic abutment through the prosthesis.
The restorative system shown in FIG. 1 and other prior abutments present numerous disadvantages. The outer portion 34 of the abutment is made of ceramic, typically aluminum oxide. Ceramic, however, is not always a desirable material for use in an abutment. Ceramics, for example, are very brittle and not easily repaired when damaged. If a ceramic component is damaged, for instance chipped, broken, or scratched, it is replaced with a new component. Furthermore, splinted, multiple-tooth ceramic prostheses are very difficult to fabricate because of the hard, brittle nature of the ceramic material. Ceramic components are also difficult to fabricate with precision because of the shrinkage of the ceramic that occurs as the ceramic material is sintered. Further yet, ceramics have a hardness even greater than that of titanium. Once these materials permanently harden, they cannot thereafter be softened and can be re-shaped only by grinding.
The prosthesis 22 is preferably made of porcelain. A porcelain prosthesis bonds well with a ceramic abutment but also is not always a desirable material. Like ceramic, porcelain cannot be easily repaired. If a porcelain prosthesis becomes chipped, for instance, it is replaced and typically not repaired. Additionally, porcelain also permanently hardens once cured. It cannot thereafter be softened and re-shaped. As a further disadvantage, porcelain has a hardness greater than natural teeth. As a result, a porcelain prosthesis will tend to wear an opposing natural tooth during chewing.
The present invention solves the problems discussed above with prior dental restorative systems and provides further advantages.
The present invention is directed toward a dental restorative system having an abutment formed from two different materials. The abutment includes a metallic core and a polymeric cuff. The core has a cylindrical configuration with an end abutting against a gingival end of a dental implant. The cuff surrounds the outer surface of the core and connects to a prosthesis. The prosthesis is also formed from a polymer and bonds to or abuts the cuff.
The present invention has numerous advantages. For example, both the cuff of the abutment and the prosthesis are made from polymer. These components can be readily repaired if they become chipped, broken, or scratched. Such a repair may occur even after the polymer is hardened and the abutment and prosthesis are placed in the mouth of a patient. Further, the polymeric prosthesis generally will not have a hardness greater than any opposing natural teeth in the patient. As such, the prosthesis will not wear or damage natural teeth as a porcelain prosthesis will. Furthermore, the polymeric cuff can be made to more closely resemble the color of natural teeth than can the traditional metal abutments. As a result, the final restoration will have greatly improved esthetics.